1. Field of the Disclosure
The present disclosure relates to a coil module including a wiring substrate and a coil electrode.
2. Description of the Related Art
FIG. 9 illustrates an existing coil module including a wiring substrate and a coil. A coil module 100 includes a wiring substrate 101, an annular coil core 102 disposed on the upper surface of the wiring substrate 101, and a coil electrode 103 that is helically wound around the coil core 102. The coil electrode 103 includes a plurality of wiring films 103a and a plurality of upper wiring conductors 103b (see Japanese Unexamined Patent Application Publication No. 8-203762 (paragraphs 0012 to 0015, FIG. 1, and others).
Each of the wiring films 103a is formed on the upper surface of the wiring substrate 102 in such a way that a first end portion thereof is disposed inside of the coil core 102 and a second end portion thereof is disposed outside of the coil core 102. The wiring films 103a are arranged in the circumferential direction of the coil core 102. Each of the upper wiring conductors 103b is a jumper wire having a substantially angular U-shape. The upper wiring conductors 103b stand on the wiring substrate 101 so as to surround the outer side surface, the inner side surface, and the upper surface of the coil core 102. A first end of each of the upper wiring conductors 103b is connected to the first end portion (located inside the coil core 102) of a corresponding one of the wiring films 103a. A second end of each of the upper wiring conductors 103b is connected to the second end portion (located outside of the coil core 102) of a corresponding one of the wiring films 103a. The upper wiring conductors 103b and the wiring films 103a constitute the coil electrode 103, which is helically wound around the coil core 102.
When the coil module 100 has such a structure, a coil can be formed without manually winding a metal wire around the coil core. Therefore, the manufacturing cost of the coil module 100 can be reduced.
In the coil module 100, the wiring films 103a and the upper wiring conductors 103b are joined to each other by using a solder. Therefore, if there is a possibility that a product including the coil module 100 is used in an environment in which temperature is higher than the melting point of an ordinary solder, the reliability of the joints between the wiring films 103a and the upper wiring conductors 103b might decrease. This may be avoided by using a high-melting-point solder or the like, which can withstand a high-temperature environment in which the product is to be placed. However, there is a problem in that, when the thicknesses of the wiring films 103a and the upper wiring conductors 103b are reduced in order to reduce the size and increase the functionality of the coil module 100, the areas of the joints between the wiring films 103a and the upper wiring conductors 103b are reduced and it is difficult to obtain a desired joint strength. Moreover, there is another problem in that it is difficult to correctly position the upper wiring conductors 103b, because the upper wiring conductors 103b, which are joined to the wiring films 103a, may fall or tilt.